Frequently asked questions

Measure the length of the window sill
To measure the length, measure the clear distance between the window reveals on the left and right (from the left window sill to the right window sill) and subtract 5 mm from each side as an installation gap.

Measure the width of the window sill
To measure the width, measure against the window frame against which the window sill will be pushed during installation. Measure the distance to the front edge of the parapet. If you want an overhang, add this on top. For external window sills, on the other hand, a projection of at least 30 mm is required for a water nose to fulfil its purpose.

An overhang is not absolutely necessary for internal window sills, but makes a big difference for visual reasons and is therefore recommended.

The window sills are manufactured in several parts from a window sill length of 3,000 mm.

The window sill must protrude at least 30 mm, but can also protrude up to 40 mm above the facade.

The respective BUG window sill edges have different deduction measurements. These must be taken into account as follows

• Clinker end piece A 150: 2.0 mm per closure
• Clinker end piece A 450: 2.0 mm per closure
• Plaster closure A 400: 2.0 mm per closure
• Plaster closure A 700: 2.0 mm per closure
• Sliding closure A 500 V: 5.6 mm per closure
• ETICS closure A 600 GS: 9 mm per closure

The hole spacing is 300 mm. The hole size is 4.2 x 7 mm.

All BUG window sills must be installed with an A2 screw including a sealing washer.

A water drainage groove is no longer necessary. Rainwater and condensation are drained away thanks to the slanted installation. Please ensure a 5° drainage slope during installation.

For windows with aluminium facing, the water drainage must be taken into account. Even if the mitre joints between the frame and the facing have seals, a capillary joint remains in the mitre joint or in the mitre gap. This property must be taken into account during installation of windows with aluminium facing, i.e. the external corners of the aluminium facing must be included in the drainage.

The tightness of the trade hole (trade hole = the area where the window, window sill, (sun protection) guide rail and facade (reveal) meet) must be ensured. The opening created here when window sills are screwed flush to the frame must be sealed with fully impregnated, pre-compressed sealing strips in accordance with DIN 18542, BG 1, Section 2.1.1 or by a suitable sealing profile against the cover frame in accordance with the "Recommendation for the installation/replacement of metal window sills (ETICS facades)" of the Gütegemeinschaft Wärmedämmung von Fassaden e. V. (Quality Association for Thermal Insulation of Facades).

In general, a second sealing level is not required if the window sill system has been tested for water tightness under heavy rain. As the tests are carried out under laboratory conditions and not on a building site, these conditions cannot be guaranteed in a real installation on a building site. Therefore, a second sealing level is always recommended for aluminium external window sills. This collects any water that penetrates the first sealing layer on the second sealing layer and drains it to the outside in a controlled manner. The second sealing layer can be created using a trough-shaped building sealant membrane or suitable plaster, filler or liquid sealant under the window sill and on the reveal.

*In stock in Austria

Window sill brackets must always be used for window sills with a projection of 150 mm or more. No window sill brackets are required below this projection. The distance between the window sill brackets depends on the length of the window sill. The distance from the outside is 400 mm. After that, a hold-down bracket must be installed every 1,000 mm.

• For a masonry projection of less than 160 mm, a central bracket is required at a distance of 1,000 mm.
• For a wall projection >160 mm, a central bracket is required at a distance of 600 mm.

Find out more here.

From a window sill projection of 150 mm, appropriate hold-down brackets must be used for thermal insulation composite systems (ETICS), exposed masonry and normal plaster facades. Our range includes window sill brackets for the respective facade types.

• ETICS window sill bracket = Window sill bracket HS 500
• Plaster facade = Window sill bracket HS 500 P
• Exposed masonry = Window sill bracket HS 500 K

It is important to observe the distances between the window sill brackets in relation to the window sill length.

BUG window sills are made of aluminium. Both the STANDARD window sill and the SOFTLINE PLUS window sill are made of EN AW-6060 alloy.

The EN AW-6060 alloy is ideal for window sills due to its material properties. This means that BUG window sills are particularly durable, safe and environmentally friendly, as our alloys are made from secondary aluminium.

The thermal expansion of pure aluminium is 1.2 mm per metre. The thermal length change is calculated as follows

• Light-coloured window sills +/- 1.3 mm per metre
• Dark window sills +/- 1.7 mm per metre

This thermal expansion factor is based on all drill holes, window sill edges and butt connectors.

For a butt connector, 4 mm must be included.

Yes, it is recommended to fit the window sill with a sound-dampening strip to reduce noise.

It is advisable to cover at least 1/3 of the window sill with sound-dampening strips.

Note: Tenders often require 2/3 of the window sill to be covered with adhesive strips.

In principle, window sill edges and butt connectors must be sealed. With BUG, this is only necessary for clinker and plaster closures and the ETICS closures A 600 GS, as the window sill sliding closures A 500 V and the butt and corner connectors H 500 D (with 90° and 135° angles) have their own sealing function.

For aluminium edge profiles for external window sills that are not sliding closures, sealing and expansion tape must be attached to the front and top when they are plastered. This prevents damage to the plaster and the masonry.

We recommend out window sill sliding closure A 500 V. The A 500 V’s unique system function is particularly noteworthy. The window sills must be installed and sealed in combination with the window sill edges in accordance with the ETICS manufacturer’s specifications.

According to the statutes, a minimum width of 18 mm or 22 mm must be maintained.

No, there is no law. However, there is a guideline that defines and describes the specific installation of aluminium window sills. This guideline serves as a basis for installation and as a basis for assessment in the event of complaints for assessors and experts.

"Guidelines for the planning and installation of windows and front doors for new buildings and renovations" (March 2020 edition), ISBN: 978-3-00-063548-9

Aluminium window sills and window sill edges must always be water tight under heavy rain if there is no second sealing level.

Roller shutter guide rails can be integrated into the window sill edge if it is ensured that the roller shutter rail is drained within the trough-shaped design of the window sill system, that water is drained exclusively via the window sill system and that no water can penetrate the adjacent facade.

No, the roller shutter guides must not run flush. They must run in front of the window sill edges. There must be a maximum of 8 mm between the aluminium window sill and the roller shutter guide.

The exception is when roller shutter guides are notched. In this case, the guide groove must run next to the window sill edges so that any water can be drained away to the window sill. A special end cap must be used for the roller shutter guide rails in this case.

The window sill edges must be notched so that drainage always takes place within the ends onto the window sill. It must be ensured that no water can penetrate the facade at the sides.

The window sill protection film applied at the factory should not remain on the window sill installed on the building for longer than 3 months. Coarse paint, mortar or plaster residues must be removed immediately. This also applies to surfaces covered with film.

We recommend thorough cleaning after assembly of the components and cleaning intervals according to the level of pollution. Wash anodised surfaces with warm water. To improve the cleaning effect, you can add a chlorine-free wetting agent to the water. If the surface is severely soiled, we recommend using special anodised surface cleaners.

You can also clean coated surfaces by washing with warm water. Again, you can add a wetting agent to the water to improve the cleaning effect. After cleaning with cleaners containing wetting agents, rinse thoroughly with clean water. Even if surfaces are severely soiled, do not use abrasive cleaners. Suitable cleaning agents are painted surface cleaners and polishes sold as vehicle cleaning products. The application can be carried out according to the recommendations of the cleaning product manufacturer.

For more information, see Aluminium Information Sheet A 05, Cleaning Aluminium in the Construction Industry, published by Aluminium Deutschland e. V. (AD), previously Gesamtverband der Aluminiumindustrie e. V. (GDA).

Retrofitting or replacing edge profiles is usually not possible without interfering with the adjacent facade and should therefore be avoided if possible. Please contact us directly so that we can find a solution to your problem based on the individual circumstances.

The A 500 V sliding closure is designed to allow the integration of guide rails for roller shutters, sun protection or insect screens by simply cutting a slot in the housing. This can also be done on site at the construction site. No time-consuming notching is necessary. This is not possible with the A 900 G. Here, guide rails must always be placed inside the end pieces.

The window sill edge profile is a sliding closure. This means that the thermally induced change in length of window sills is partially absorbed by this seal. The A 500 V also offers the option of easily integrating guide rails for roller shutters, sun protection or insect screens with a separating cut in the end cap.

A seal must always be installed between the screw plate of the window sill and the window element or connection profile. The type of seal is not defined in the regulations. The installer is responsible for ensuring that the seal functions properly in the long term. The AD 500 window sill screw-on seal is a system-tested solution for this purpose.

Installation in the lower grooves of window profiles is generally not recommended, as sealing in the corner areas cannot be guaranteed. Water can therefore enter the facade in this way, especially when exposed to rain and wind at the same time.

Wood-aluminium windows protect the wood from weathering with their aluminium shell on the outside. This also makes them significantly easier to care for. If you still want the wood effect, you can finish the aluminium frame profile with a wood decor.

With wooden windows, weather protection or weather protection rails can always be integrated. It is also possible to provide existing wood windows with an aluminium shell from BUG on the outside. Information about possible processors can be found on the "Find specialist dealers and processors" page.

All colour spectra can be implemented for aluminium profiles for the frame. RAL colours, anodised finishes and decorative surfaces can all be used for mechanically manufactured frames. Special colours at extra cost.

Yes, you can order your own profile constructions from us if you purchase the minimum press batch size. Please contact the relevant expert for wood-aluminium systems.

Our delivery times vary depending on the depth of processing. Welded frames have a delivery time of approx. 4 weeks from technical approval. The delivery time for mechanical frames is approx. 6 weeks.

The maximum size of welded window frames is 2,600 x 5,990 mm. With mechanical aluminium frames, a maximum size of 5,900 x 5,900 mm can be implemented. Please note that technical and transport difficulties may occur with this frame size.

The UW values vary depending on the type of wood used in the glass. With the use of 0.5 mm glass, a UW value of up to 0.67 can be achieved with our low-E wood-aluminium systems. Additional information can be found under BUG low-energy solutions.

Yes, we at BUG Aluminium-Systeme offer tested and certified glass fall protection. The BUG FrontProtect is quick and easy to install. This system uses a frame-integrated design with concealed fixings.

At the customer’s request, your ordered window frames can be delivered on transport racks. You keep the transport racks for the time being, and our transport company will take them back with them when they deliver the BUG window frames next time. This means that there is no additional work or cost involved in disposing of the transport racks due to their multiple use.

We are happy to supply mechanically manufactured aluminium frames with our film. Please indicate this explicitly when ordering.